MAC + PHY Modeling & Multilayer Simulation of DSRC V2V Network

Transcription

1 MAC + PHY Modeling & Multilayer Simulation of DSRC V2V Network Cynthia Cudicini - MathWorks 2015 The MathWorks, Inc. 1

2 Vehicular Communications Vehicle-to-Vehicle (V2V) Vehicle-to-Infrastructure (V2I) Vehicle-to-Pedestrian (V2P) Vehicle-to-Network (V2N) V2X Continuous, high-speed, and authenticable safety data exchange among moving vehicles (V2V) and between vehicles and roadway infrastructure (V2I), pedestrians (V2P) and cellular network (V2N) 2

3 Motivations for V2X Safety 33,000 death in highway accidents (US DOT, 2012) 5.1 million crashes (US DOT, 2012) Leading cause of death for people of age Mobility & Productivity 5.5 billion hours of traffic delay (per year) 121 billion USD cost of urban congestion (per year) Environment 2.9 billion gallons of waste in fossil fuel (per year) 56 billion lbs. of additional emitted CO2 3

4 Impact of V2X technology US DOT NHTSA: If V2X technologies alone are widely deployed, they have the potential to address 81 percent of light-vehicle crashes V2X based on cooperative communications Extends the safety features offered by Advanced Driver Assistance Systems (ADAS) technologies RADAR LiDAR Video processing 4

5 V2X Safety Applications 5

6 Proposed V2X Technologies 1. Dedicated Short Range Communications (DSRC) 2. Cellular Vehicle-to-Any-Device communications (C-V2X) Operating at 5.9 Gigahertz (GHz) band Strict performance requirements - Latency: Less-than-100-ms delay - Range: Up to 300 meters - Supported speeds: Typical highway velocities Using Basic Safety Messages (BSM) data exchange 6

7 Basic safety messages (BSM) & algorithm development Position information Velocity information Acceleration information Size information 7

8 What you will learn today How to model, simulate, visualize V2X safety applications: 1. Visualize and model traffic scene and vehicles in motion 2. Apply equations of motion to handle vehicular maneuvers, collision prediction, collision avoidance and after-collision trajectory algorithms 3. Simulate IEEE p physical layer of DSRC standard for V2V communications 4. Simulate IEEE MAC layer of DSCR standard at the same time as the PHY 8

9 Example: p V2V Safety Scenario Simulation 9

10 Implementation MATLAB User Interface wifinet Network specifications wifisim Network simulator Simulation Artifacts wifistation wifistation wifistation Multilayer simulation of a WiFi station Multilayer simulation of a WiFi station Multilayer simulation of a WiFi station wifista wifista wifista Station specifications Station specifications Station specifications Simulink User Interface PHY TX DCF (CSMA/CA) PHY RX waveform2psdu Convert waveform to PSDU wifilib WiFi block library psdu2waveform Convert PSDU to waveform waveformaggregate Simulate interference Legend MATLAB structure MATLAB function MATLAB object (incl. System object) Simulink library wifichannel Manage all links on a shared channel wifilink wifilink wifilink One-way PHY link & noise One-way PHY link & noise One-way PHY link & noise 10

11 PHY design made easy with WLAN System Toolbox 11

12 MAC and CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) Media Access Control (MAC) a set of rules that coordinate stations to share common bandwidth efficiently uses CSMA/CA method for both Ad-hoc (or IBSS) mode, and Infrastructure mode CSMA/CA includes 2 mechanisms Basic access RTS/CTS (Request To Send/Clear To Send) 12

13 Simulate Interference of Multiple Bursts of Waveforms Receiver hear time-shifted aggregation of waveforms An illustrative example Collision/Interference RX2 TX3 TX2 TX1 13

14 CSMA/CA Basic Access Source station states 1. Carrier sense (DIFS) 2. Random back-off 3. Transmit data 4. Turn-around (SIFS) 5. Wait/receive ACK Other station Virtual carrier sensing Listen/read duration field of MAC headers, set NAV (Network Allocation Vector) counter as indicator of channel busy 14

15 How RTS/CTS Resolve Hidden Terminal Problem CSMA basic access cannot avoid the collisions due to hidden terminal problem 1 is sending data to 2 3 is out of range of 1, therefore believes channel free 3 sends data to 2 and causes collision RTS/CTS can help 1 sends RTS (Request To Send) to responds with CTS (Clear To Send) CTS heard by both 1 and 3 1 starts to send data 3 detects CTS is for others, and set NAV 15

16 CSMA/CA with RTS/CTS Source station states 1. Carrier sensing (DIFS) 2. Random back-off 3. RTS 4. Turn-around (SIFS) 5. Wait/receive CTS 6. Turn-around (SIFS) 7. Transmit data 8. Turn-around (SIFS) 9. Wait/receive ACK NAV of RTS/CTS covers entire data transmission 16

17 Re-transmission Increase retry counter Doubles Contention Window (CW) up to CW_max Backoff counter = random number between [0, CW] Initial attempt: CW = CW_min Drop the frame when: Retry counter > Retry_max Example re-transmission configuration CW_min = 31, CW_max = 1023, Retry_max = 6 17

18 Multilayer Simulation Enable MAC/PHY Co-Design Constellation diagram for frames with and without collisions PHY simulation of creation, transmission, interference, reception and recover of a VHT frame MAC simulation of multiple, independent stations with self-managed DCFs Support both MATLAB command-line and Simulink graphical modeling/simulation 18

19 DEMONSTRATION 19

20 Alternative Approach to Model/Simulate MAC Behaviors 20

21 Summary - MATLAB and Simulink provide: Framework for multilayer, multi-nodes network simulation Simulate interference of multiple, independent bursts of waveforms on a shared channel Help network design, diagnose, analysis, and performance evaluation Plug-in MAC and PHY components of different types System object (MATLAB) based or Stateflow-based MAC Any PHY waveform generator (802.11, LTE, ) Visualization tools to build meaningful scenarios Supports code generation as a next step for implementation 21